1. Field of the Invention
The present invention relates to a method of manufacturing a palladium (Pd) thin film, and more particularly, to a method of manufacturing a Pd thin film having increased activity of surface enhanced Raman scattering (SERS) by using an electroless-plating method.
2. Description of the Related Art
Generally, a palladium (Pd) thin film is manufactured by using one of three methods, i.e., an electroplating or electro-deposition method, a vapor deposition method, and an electroless-plating method.
In the electro-deposition method, elaborate and expensive equipment is required to guarantee deposition at an accurate ratio and a suitable electric potential. Moreover, in the electro-deposition method, an electric contact should be performed on a plating surface. In addition, not only a long time is taken for such an electric contact if an integrated circuit (IC) having a very complex circuit pattern, specially a certain high density, is used, and also it is difficult to manufacture a thin film. Furthermore, a surface that is plated should be conductive, and should be connected to an external power source, such as a voltage source or a current source.
Also, even the vapor deposition method has a few intrinsic weaknesses. In various application fields, elaborate and high vacuum equipment is required, and a large amount of Pd metal is consumed during an evaporation process. However, it is difficult to attach evaporated Pd only to a selected area in a plated surface. In other words, it is not easy to design a pattern having Pd by using the vapor deposition method.
Meanwhile, effects of surface enhanced Raman scattering (SERS) may increase according to changes in a surface or structure of a metal. A technology using such SERS is applied to various fields, for example, chemical analysis, corrosion, lubrication, catalysis, sensor, and molecular electronics.
However, SERS shows a large effect when a noble metal, such as gold (Au), silver (Ag), or copper (Cu) is used, and such a limitation hinders SERS from being variously used.
However, it is recently proven that SERS is active even in a transition metal if roughening is suitably adjusted. However, it is difficult to obtain a Raman spectrum of molecules under a non-electrochemical environment, in detail, in a transition metal, such as platinum (Pt) or Pd.
Accordingly, KR 10-2004-0106238 discloses an Ag electroplating method using Pt-Ag activation method. Here, a core without a seed layer is generated on a substrate having a high specific resistance during a semiconductor metal wire process such that electroplating is possible via an activation method, and then Ag electroplating is performed to form a uniform Ag thin film without a defect such that Ag having a low specific resistance is used as a material for a highly integrated semiconductor wire process.
Although a general electroplating method discloses an electric gilding method using Pd, but a thin fill is still formed by using electricity, and the thin film cannot be formed on an insulating substrate.